Uric acid is a natural waste product created when the body breaks down purines. Measuring the amount of uric acid in the blood is a common part of laboratory testing during pregnancy. This provides healthcare providers with information about a pregnant person’s metabolic health and kidney function. Interpreting the result requires understanding how the body’s normal physiology changes throughout gestation.
Basic Physiology of Uric Acid
Uric acid is produced as the final product of purine metabolism, primarily in the liver. Since purines are components of DNA and RNA, they are constantly being broken down and reformed. The concentration of uric acid in the blood represents a balance between production and elimination.
In non-pregnant adults, serum uric acid levels are maintained between 2.5 and 5.6 mg/dL. The kidneys handle elimination, filtering the substance out of the blood and excreting about two-thirds of it in the urine. The remaining portion is eliminated through the digestive tract. A sustained elevation above this range is defined as hyperuricemia, but this baseline shifts in a healthy pregnancy.
Defining Normal Ranges Across Trimesters
A healthy pregnancy causes a decrease in uric acid levels during the initial months. This drop is driven by an increase in the glomerular filtration rate (GFR), the rate at which the kidneys filter blood. Increased blood volume and renal blood flow make the kidneys more efficient at clearing uric acid from the bloodstream.
This increased renal clearance, along with the uricosuric effect of estrogen, causes serum levels to be lowest in the first trimester, frequently falling to 3.0 mg/dL or below. Normal reference ranges for the first trimester are often cited as being between 2.0 and 4.2 mg/dL. As the pregnancy progresses into the second trimester, the normal range may slightly expand, cited between 2.4 and 4.9 mg/dL.
Uric acid concentration begins to gradually rise again in the third trimester, remaining below the non-pregnant baseline. Normal levels near term fall within the range of 3.1 to 6.3 mg/dL. This increase is considered normal and results from the rising demands of the growing fetus and placenta, and a slight decline in renal clearance later in the pregnancy.
Hyperuricemia and Associated Pregnancy Conditions
When uric acid levels exceed the established normal range for a given trimester, the condition is termed hyperuricemia. This elevation is associated with hypertensive disorders of pregnancy, most notably preeclampsia. Preeclampsia is characterized by high blood pressure and signs of damage to another organ system, usually the kidneys, which often manifests as protein in the urine.
Elevated uric acid is one of the earliest and most consistent laboratory findings in pregnancies affected by preeclampsia, often appearing before the traditional symptoms of hypertension and proteinuria. The increase is thought to be a marker of reduced kidney function and increased cellular stress within the placenta and maternal vasculature. In some clinical settings, a measurement of 5.2 mg/dL or higher in the second half of pregnancy has been identified as an indicator for the diagnosis and prognosis of preeclampsia.
The degree of uric acid elevation often correlates with the severity of the hypertensive disorder and can be a predictor of adverse fetal outcomes. These adverse outcomes can include preterm birth and the delivery of a small-for-gestational-age infant. While hyperuricemia is considered a marker reflecting the underlying disease process, evidence suggests that the uric acid itself may contribute to the condition by promoting inflammation and damaging the lining of blood vessels.
Clinical Monitoring and Testing
A serum uric acid test is not part of routine prenatal screening for an uncomplicated pregnancy. The test is ordered when a healthcare provider suspects the onset of a hypertensive disorder. This occurs if a pregnant person develops new-onset high blood pressure after 20 weeks of gestation or shows other symptoms suggestive of preeclampsia, such as headaches, vision changes, or swelling.
The testing procedure is a simple blood draw, and the results are evaluated in the context of the patient’s overall clinical picture, including blood pressure readings and other laboratory results. While the uric acid level is helpful for monitoring the severity of the condition, it is not used as the sole diagnostic criterion for preeclampsia.
Management for elevated uric acid in pregnancy focuses on treating the underlying condition that caused the rise, such as managing the patient’s blood pressure and monitoring for signs of preeclampsia progression. The goal is not to lower the uric acid level directly, but rather to manage the maternal and fetal health risks associated with the disorder. Close communication with the healthcare provider regarding the context and interpretation of the test result is important.